Hydrophobic substrate with coating receptive to inks

Abstract

A recording material, comprising a hydrophobic substrate material with a polymeric coating, has excellent receptivity for inks that do not normally wet hydrophobic substrates. The substrate material is coated with a mixture of polyvinylpyrrolidone and a compatible matrix-forming polymer. The matrix-forming polymer is a material, such as gelatin or polyvinyl alcohol, that is swellable by water and insoluble at room temperature but soluble at elevated temperatures. A transparent base sheet, such as cellulose acetate or polyethylene terephthalate, can be coated with the mixture of polymers to provide a sheet material which can be used in ink jet printers and in pen-type graphics recorders, operating at normal speeds, to record large color-filled areas without puddling, running, or wetness and with high color density and excellent resolution.

We claim: 
     
       1. A transparent recording medium for ink jet printing, comprising a transparent support layer having a substantially hydrophobic surface with a transparent surface coating receptive to aqueous inks, said coating comprising a mixture of polyvinylpyrrolidone and a compatible matrix-forming hydrophilic polymer selected from the group consisting of gelatin and polyvinyl alcohol, the ratio of polyvinylpyrrolidone to matrix-forming polymer being in the range of 1:3 to 3:1, the polyvinylpyrrolidone having a molecular weight of at least 90,000. 
     
     
       2. The recording medium of claim 1, wherein said support layer has opposed major surfaces, at least one of which is substantially hydrophobic, and both surfaces have a transparent surface coating comprising a mixture of polyvinylpyrrolidone and a compatible matrix-forming hydrophilic polymer. 
     
     
       3. The recording medium of claim 1, wherein the matrix-forming polymer is an essentially fully hydrolyzed polyvinyl alcohol having a molecular weight of less than 60,000. 
     
     
       4. The recording medium of claim 1, wherein the matrix-forming polymer is gelatin derived from pig skin. 
     
     
       5. A process for making an improved transparent ink jet recording medium, comprising the steps of providing a transparent support layer having a substantially hydrophobic surface, and   applying a transparent, aqueous ink-receiving coating to said surface, said coating comprising a mixture of polyvinylpyrrolidone and a compatible matrix-forming hydrophilic polymer selected from the group consisting of gelatin and polyvinyl alcohol, the ratio of polyvinylpyrrolidone to matrix-forming polymer being in the range of 1:3 to 3:1, the polyvinylpyrrolidone having a molecular weight of at least 90,000.   
     
     
       6. The process of claim 5, comprising the further steps of applying a transparent, aqueous ink-receptive coating to the opposite surface of said substrate, said coating comprising a mixture of polypyrrolidone and a compatible matrix-forming hydrophilic polymer. 
     
     
       7. The process of claim 5, wherein the matrix-forming polymer is an essentially fully hydrolyzed polyvinyl alcohol having a molecular weight of less than 60,000. 
     
     
       8. The process of claim 5, wherein the matrix-forming polymer is gelatin derived from pig skin.